Atom Strucuture/ Chemical Bonds

Question 1

How do you define life/living organisms?

Answer 1

compartmentalized open systems made of carbon polymers that use external source of energy to perform work and catalyze biochemical reactions to maintain their integrity (entropy) and reproduce ourselves.

Question 2

What is the similarity between living things and non-living matter?

Answer 2

We are made of the same atoms (chemical molecules)

Question 3

What is an atom composed of? What is the atomic nucleus composed of?

Answer 3

atom has nucleus in the center and electrons that orbit around the nucleus (form cloud). Atomic nucleus is made of protons and neutrons (0 charge)

Question 4

What defines an element? anther name used to describe this?

Answer 4

The number of protons in the nucleus. By its atomic number (# of protons)

Question 5

What unit is mass of an atom measured?

Answer 5

Atomic units. Mass of a proton= 1 atomic mass unit.

Question 6

Define atomic (molecular) weight.

Answer 6

The total number of protons and neutrons in the nucleus.

Question 7

What defines the size of an atom? Explain the scientist involved and his theory.

Answer 7

Electron orbitals determine size of atom (orbits is 10000x bigger than nucleus). Werner Heisenberg had THEORY OF UNCERTAINTY (1927) that said you cannot measure the position or velocity of an object exactly.

The probability density of where e- can be at the moment has the shape of a spherical cloud- which is called orbital

Question 8

What is an orbital?

Answer 8

The probability density or space of where electron will likely be (shape of spherical cloud).

Question 9

What does the size of atom tell you? How do elements differ and what does it indicate?

Answer 9

The larger the atom, the more protons, neutrons and electron it has. elements differ by number of protons and electrons it has. Indicates ability to interact with other elements in chemical rxns.

Question 10

What are Isotopes?

Answer 10

atoms with the same number of protons but different number of neutrons.

Question 11

What are radioactive isotopes? How many Isotopes does Hydrogen have? What are they? Which of the isotopes are radioactive?

Answer 11

isotopes that have unstable nuclear imbalance and require radioactive decay. Hydrogen has 3 isotopes: PROTIUM (H1, o neutrons), Deuterium (H2, 1 neutron), and Tritium (H3,2 neutrons radioactive isotope)

Question 12

Give examples of other radioactive isotopes.

Answer 12

Carbon 14 (2 extra neurons), Phosphorus (P 32 1 extra n; P33 2 extra n).

Question 13

What is a half life? how many half lives does Carbon-14 have?

Answer 13

Half life is the period of time for 50% atoms decayed. Carbon-14 has 5730 years in half life.

Question 14

What is radioactive decay?

Answer 14

breakdown of unstable nucleus by losing energy (radiation) and allowing nucleus to be be balanced wit p + n and stable.

Question 15

How can you apply Isotopes to cell and molecular biology as well as medicine?

Answer 15

use isotopes for RADIOAUTOGRAPHY- technique used by X ray film to visualize molecules or fragments that have been radioactively labeled. Ex; incorporating amount of radioactive phosphorous into RNA and DNA to analyze length of DNA fragments (footprint of RNA protein)

In medicine- isotopes can be used in RADIOLOGY AND NUCLEAR IMAGING. EX: PET SCAN (uses F-18 glucose to detect abnormal glucose metabolism and detect tumors or cancers; also monitor response of chemotherapy to malignancy).
NUCLEAR HEART SCAN- uses TI-201 (thallium-201 pharmaceutical used in diagnosing and localizing myocardial infarctions) ; THYROID SCAN- uses I-135 (radioactive iodine salt to detect thyroid cancers or destroy overactive cells in thyroid gland)

Question 16

What is a periodic table? What does it tell you?

Answer 16

table that lists all the elements by increasing atomic number. It tells you an element’s atomic weight (mol weight of substance), atomic number. It shows the masses of the most stable, more ubiquitous isotopes.

Question 17

How many electrons can occupy the same orbital? Describe their orientation.

Answer 17

2 electrons. Paired electrons have opposite spins ( opposing magnetic fields by each moving e- . Ex: one moves clockwise, other counterclockwise

Question 18

Explain the process of completing electron shells? Describe the different electron shells in order and how many orbital they each have

Answer 18

you must finishing completing the electron shells closest to the nucleus before occupying next higher orbitals or shells. The elements with all of their electron shells completed are the most stable. first shell is S which is small and has one orbital (hold 2 electrons). 2nd, 3rd, 4th electron shells have 4 orbitals (S, px, py, pz) that can have total of 8 electrons.

Question 19

What is the s orbital? P orbital? How are orbitals arranged

Answer 19

S orbital is sharp. P orbital is principal. orbitals are arranged into layers or shells, depending how far or close to the nucleus.

Question 20

what determines the stability of an atom?

Answer 20

completion of electron shells (all shells are fully completed).

Question 21

How do atoms form molecules?

Answer 21

Through covalent bonds between each other. e- from two H atoms occupy each other’s orbital, mutually completing e- shell and forming molecule of H2
one shared pair of e- forms one covalent bond
molecular hydrogen (each atom accepts an e- from other and donates their own)
mutual stability- achieved by sharing e-.

Question 22

describe the three types of chemical bonds between atoms.

Answer 22

Covalent bonds (sharing of electrons between nonmetals), Metallic bonding and Ionic Bond (electrostatic attraction between metals and nonmetals)

Question 23

What defines the chemical properties of elements?

Answer 23

the number of electrons on each shell (or how full a shell is) define chemical properties. The physical and chemical properties change periodically.

Question 24

Which elements in periodic table are classified as radioactive (unstable) ?

Answer 24

Elements after atomic number 83

Question 25

Which chemical bond is the strongest between atoms?

Answer 25

Covalent bonds

Question 26

Why do atoms form bonds?

Answer 26

to complete electron shells (through sharing or transfer of e-) and become stable

Question 27

Describe Covalent bonds and discuss what makes them unique.

Answer 27

Covalent bonds occur when electrons are SHARED between atoms, and form MOLECULES as a result of atoms connecting through covalent bonds. Sharing electrons may provide MUTUAL STABILITY between 2 atoms (completion of shells). Covalent bonds must also maintain certain distance between atoms (not too close or too far; avoid repulsion, or no attraction at all) Bond lenght: 0.074 nm

Question 28

which 4 elements in periodic table serve as backbones of biomolecules? What kind of elements are biomolecules made of?

Answer 28

H, C, N, O; biomolecules made of non metals with maximum 3 electron shells.

Question 29

What are valence electrons?

Answer 29

Valence electrons are those e- in the outermost shell that can be shared and hence form covalent bonds.

Question 30

Provide an example of how molecules form through covalent bonding.

Answer 30

Ex: molecular Hydrogen. You have 2 Hydrogen atoms and electrons from each of those H atoms, will occupy each other’s orbital (each atom accept e from other, and donate their own) mutually completing electron shell and forming molecule of Hydrogen, H2. each shared electron pair forms one covalent bond.

Question 31

Provide two common examples of elements who form covalent bonds.

Answer 31

2 atoms of chlorine will form a chlorine molecule through one covalent bond and stabilize its electron shell. Oxygen molecule using 2 atoms of Oxygen forms TWO covalent bonds to stabilize its electron shell. each atom completes shell by adding 2 e- to its 2 orbitals.

Question 32

What are nonmetals? what are their properties? List examples.

Answer 32

Nonmetals are elements which have nearly or fully completed electron shells. Properties are:

1. molecules have definitive number of atoms
2. low density (gases, liquids, powders)
3. They do not conduct electricity.
   ex: Sulfur, phosphorus, bromine

Question 33

What are noble gases? Atomic gases?

Answer 33

Noble gases are elements with completed outer electron shells who are stable on their own and do not form molecules. In their pure form they are atomic gases and cannot perform chemical reactions. Ex: He, Neon, Ar.

Question 34

What are nonmetals? what are their properties? List examples.

Answer 34

Nonmetals are elements which have nearly or fully completed electron shells. Properties are:

1. molecules have definitive number of atoms
2. low density (gases, liquids, powders)
3. They do not conduct electricity.

Question 35

Compare and contrast Asymmetrical and Symmetrical covalent bonds.

Answer 35

Asymmetrical covalent bonds- 2 atoms interact and the pair of shared e- shifts toward more electronegative atom, causing dipole or unequal sharing of e-, separate positive and negative charges. Ex: CO2, NO, HCl, have asymmetric covalent bonds. the shift in electron density of water causes polarization.
Symmetric covalent bonds- equal sharing of electrons, like Cl2 and O2 molecules.

Question 36

Describe ionic bonds. provide an example.

Answer 36

Ionic bonds- electrostatic attraction between two ions of opposite charge. occurs between metals and nonmetals. Ex Like NaCl (table salt). Chlorine will accept e- from Na to complete its electron shell, leading to dissociation of NaCl into 2 separate ions. Nacl goes to Na+ and Cl- [cation (+) and anion (-) ]. NaCl has a crystal structure and is stabilized by ionic bonds. no molecules in pure Nacl.

Question 37

Compare and contrast Asymmetrical and Symmetrical covalent bonds.

Answer 37

Asymmetrical covalent bonds- 2 atoms interact and the pair of shared e- shifts toward more electronegative atom, causing dipole or unequal sharing of e-, separate positive and negative charges. Ex: CO2, NO, HCl, have asymmetric covalent bonds.
Symmetric covalent bonds- equal sharing of electrons, like Cl2 and O2 molecules.

Question 38

Describe ionic bonds. provide an example.

Answer 38

Ionic bonds- electrostatic attraction between two ions of opposite charge. occurs between metals and nonmetals. Ex; when a alkali metal interacts with halogens, e- c loud shifts toward nonmetal nucleus. Like NaCl (table salt). Chlorine will accept e- from Na to complete its electron shell, leading to dissociation of NaCl into 2 separate ions. Nacl goes to Na+ and Cl- [cation (+) and anion (-) ]. NaCl has a crystal structure and is stabilized by ionic bonds.

Question 39

compare and contrast three types of chemical bonds.

Answer 39

Ionic bond- form between metals and non metals, atoms with different electronegativity
covalent bond- sharing of electrons; symmetrical and asymmetrical. only nonmetals
Metallic bonding- between atoms of metal with few atoms in outers shell.